1. Field of the Invention
The present invention is related to the field of energy controlling circuitry used to control the provision of energy to electromagnetic coils. More particularly, the present invention relates to that portion of the above-described field in which energy is provided in discrete, timed pulses for controlling the delivery of fuel to an internal combustion engine. Specifically, the present invention relates to the control of energy used by and dissipated by the electromagnetic coils of the various electromagnetic injector valves.
2. Summary of the Prior Art
The prior art teaches that the electromagnetic injector valves of electronic fuel control systems are connected through suitable power amplification stages directly to the output of the main computing circuit so that they are intermittently energized in conjunction with the occurrence of pulses which represent the instantaneous fuel requirement for the associated engine. Due to the fact that the output of the voltage regulator, which is in the charging circuit of the vehicle battery, is capable of relatively wide variations in the magnitude of the voltage output, the prior art has taught various ways of detecting the instantaneous level of voltage available to energize the injectors and of adjusting the duration of the injection control pulses computed by the main computing circuit to provide that the total amount of fuel injected during the injector open cycle is substantially uniform for constant engine operating conditions and varying voltages applied to the injector valves. An example of such an elaborate compensation scheme may be found in recently issued U.S. Pat. No. 3,483,851 issued to Wolfgang Reichardt and presently assigned to Robert Bosch G.m.b.H. Such elaborate compensation schemes add greatly to the cost and complexity of the main computing circuit and furthermore introduce potential additional errors in accuracy in view of the fact that the additional circuitry to control pulse length inherently introduces factors which may vary during the life of the system and may vary from system to system. It is, therefore, an object of the present invention to provide a system for controlling the injector valve energization which does not influence, or affect, the main computing circuitry. It is furthermore an object of the present invention to provide a means for controlling injector valve energization which does not require a compensation signal to be applied to the main computing circuitry. It is a still further object of the present invention to provide a means for controlling injector valve energization which eliminates the influence of variations in voltage regulator output signal currently experienced by present electronic fuel control systems.
It is widely acknowledged within the art that one of the difficulties encountered in fuel injection systems arises from the fact that, while energizing pulses may be made substantially rectangular in configuration, injector valve response is relatively sluggish so that the valve opening characteristic is far from rectangular. As a consequence, the calculation of fuel injected by a valve having this nonrectangular opening response is rather complex, and furthermore, total quantities of fuel are reduced below that which could ordinarily be injected if the valve had a rectangular response characteristic. It is, therefore, an object of the present invention to provide a means of controlling the injector valve energization which permits more rapid valve opening characteristics to therefore provide a valve opening response which is more closely rectangular than presently achieved by the teachings of the prior art. It is a still further object of the present invention to provide a means for controlling injector valve energization so that valve closing may be facilitated by reducing the total amount of energy stored in the electromagnetic field.
The prior art systems for energizing the injector valve means electromagnetic coils used the maximum available voltages to attempt to open the injector valves as rapidly as possible. In fact, the prior art teaches various techniques for over-energizing such valves to voltages substantially above the maximum available. All of these approaches cause substantial current flow through the electromagnetic coils in steady state operation. In order to reduce the requirement for the electromagnetic coils to dissipate large amounts of energy, high value resistances were placed in series with the electromagnetic coils as energy dissipating devices. These resistances were costly to incorporate due to their high energy dissipation requirement. Furthermore, they tended to defeat original objectives whose implementation produced their requirement. It is a specific objective to provide a means of improving injector valve opening times which does not require a high value series resistance. It is a more specific object of the present invention to provide a system for energizing the injector valve means electromagnetic coils which applies a lower level of voltage to the electromagnetic coils but which results in improved valve opening times.